Sewing machine having needle thread tensioning device



Oct. 14, 1969 F. GEGAUF SEWING MACHINE HAVING NEEDLE THREAD TENSIONINGDEVICE Filed Dec.

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A TTUFA/EYJ' United States Patent c SEWING MACHINE HAVING NEEDLE THREADTENSIONING DEVICE Fritz Gegauf, Steckhorn, Switzerland, assignor toFritz Gegauf Aktiengesellschaft, Bernina-Nahamaschinenfabrik, Steckborn,Switzerland Filed Dec. 5, 1966, Ser. No. 599,318 Int. Cl. D05b 47/02;B65h 59/22 US. Cl. 112254 5 Claims ABSTRACT OF THE DISCLOSURE Theinternal construction of the tensioning device is shown in sectional andplan views and its orientation on the sewing machine is indicated. Thetensioning device comprises a relatively small-sized unit which includestensioning disks which are biased together under the force of a spring,the setting of which may be varied by a control knob which is visibleand operable from the front of the device on the sewing machine. Thesewing thread is passed from a thread giver downwardly around a mountingshaft for the tensioning disks so that it will be looped between thetensioning disks during the operation of the machine. The mechanism forthe regulation of pressure on th tensioning disks between which theneedle thread is passed and the spring regulator for engaging the threadand taking up any slack therein are built one into the other. A knob foreffecting proper tensioning control provides an adjustment of atensioning nut which is mounted on a threaded end portion of the diskshaft. The nut is restrained against rotation with the disk shaft by aprojecting cam which is formed as an extension of a collar or housingmember which surrounds the disk shaft so that the nut will advance alongthe disk shaft when it is rotated by the knob. The nut bears against acoiled tension regulating spring which causes the collar to bear againstthe disk plates with a selected amount of pressure in accordance withthe setting of the control knob. The collar is provided with a recess inone end face to accommodate the tension regulating spring.

A further feature which is illustrated and described is the arrangementof a coiled thread regulating spring which is carried in an axiallyextending recess in an appropriate end face of the collar which iscarried on the disk shaft. The spring member includes an end loopportion which extends around the periphery of the tensioning disks sothat when a thread is engaged between the disks, the thread willnormally pick up this loop end of the spring and the spring will providesome tensioning effect on the thread to take up any slack therein.

SUMMARY OF THE INVENTION The known thread tensioning devices which areemployed with sewing machines and which employ tensioning disks arearranged on the side of the arm head facing the operator at a locationbelow the lowest position of the thread giver. Such devices have greatstructural height and therefore they interfere with the clear view ofthe operator of the material being sewn. This structural height is dueto the fact that the tensioning devices are con- 3,472,190 Patented Oct.14, 1969 structed in a manner such that the thread regulator is arrangedbehind the thread tensioning disk and the tensioning device for theproduction of pressure on the needle thread is arranged before thesedisks. In order to accommodate the thread tensioning device on themachine, the sewing machine housing usually possesses an eye for theuptake of the holder part of the tensioning device so that thestructural height is additionally increased. In order to avoid thedistadvantages of tensioning devices which obstruct the view of theneedle, it has been proposed to separate the thread tensioning deviceand the thread regulator and to arrange only the regulator below thethread giver. The tensioning device for the needle would then bearranged either at the front of the machine or the greatest possibledistance above the regulator or at the back of the sewing machine arm oreven on the rear end thereof. All of these expedients lead to poorersewing results due to the fact that the thread must be guided overexcessively long and varied guiding paths and especially because of thelong thread path which is required from the tensioning device to theneedle. Such a long guide path is highly disadvantageous especially withrespect to synthetic threads because of their plastic deformation.

In accordance with the present invention there is provided aconstruction in which the thread tensioning device and the regulatorare. arranged so that they can be attached below the lowermost positionof the thread giver without disturbing the field of vision. For thispurpose the device according to the invention is characterized in athread tensioning device in which the mechanism for producing thepressure on the needle thread and the regulator for the thread are builtone into the other. The construction is such that the thread tensioningdisks and the regulator disk project from the sewing machine head at alocation at which the field of sewing will remain unobstructed from theoperators view.

An object of the invention is to provide a sewing machine having an armhead which overlies a lower sewing base and which carries the sewingneedle with a thread regulating and tensioning device mounted on thehead directly below the thread giver so that the thread may be easilypassed between the tensioning disks of the device and which includesmeans for regulating the tension on the thread and for effecting theautomatic release of the tension through the operating mechanism of thesewing machine.

A further object of the invention is to provide a thread tensioningdevice of simple and compact construction with a coiled spring forregulating the engaging force on a pair of tensioning members for thethread arranged in a recess of one end face of a collar or housingmember and a spring having a torsion arm portion engageable with thethread for taking up any thread slack which is disposed in a recess inthe opposite end face of the housing.

A further object of the invention is to provide a thread tensioningdevice for a sewing machine which is simple in design, rugged inconstruction and economical to manufacture.

BRIEF DESCRIPTION OF THE DRAWING VIEWS In the drawings:

FIG. 1 is an end elevational view of a sewing machine having atensioning device constructed in accordance with the invention;

FIG. 2 is a partial side elevational view of the sewing machine of FIG.1;

FIG. 3 is an enlarged axial sectional view of the thread tensioningmechanism;

FIG. 4 is a section taken on the line 4-4 of FIG. 3; and

FIG. is a top plan view of the tensioning device alone.

DETAILED DESCRIPTION Referring to the drawings in particular, theinvention embodied therein comprises a sewing machine generallydesignated 1 which includes an arm head portion 2 which overlies asewing table 50 of a base portion 52.

In accordance with the invention, a thread tensioning and regulatingdevice generally designated 54 is mounted on the arm head 2 below thelowermost position of a thread giver 3. A regulating disk or knob 4 forthe tensioning device is located as indicated so that it will be readilyvisible to the eye of an operator without interfering with the operatorscomplete view of the table 50 and the material being sewn thereon. Thebroken lines 8 and 9 in FIG. 1 indicate the normal range of view of anoperator and shows how this view would not be obstructed by the locationor construction of the regulating or tensioning device 54. A needle bar5 with a needle holder 6 and a needle 7 is arranged in a known mannerwithin the arm head portion 2 to extend downwardly in a position tooverlie this sewing table 50.

The arm head 2 has a housing which is provided with an opening toaccommodate the thread tensioning device. The tensioning device includesa housing or collar member 11 which is secured in the opening againstrotation by a pin 14 which permits axial displacement by an amount whichmay be regulated by the frictional drag of a set screw 15. The collar 11is provided with a central bore in which is slidably located atensioning bolt or disk shaft 12. A regulating disk or knob control 4 issecured to the bolt by means of an adjustable screw 13. After adjustmentof the screw 13, it is covered from view by means of a flexible platemember 56.

The thread tensioning bolt 12 is provided with an extension portion orthreaded end 16 on which is arranged a tensioning nut 17 which islocated on the interior of the housing of the arm head 2. The nut 17 isprovided with an opening or slot through which extends a projection orcam portion 18 of the collar 11 so that the nut is prevented fromrotating in respect to the tensioning bolt 12. The interior end face ofthe collar 11 immediately surrounding the cam projecting portion 18 isprovided with an annular recess 20 which accommodates one end of a coilspring 21 which bears at its opposite end against the nut 17.

The regulating disk 4 covers tensioning disks 22 and 23 which arecarried on the tensioning bolt 12 on each side of an intermediate disk24. The disk 23 abuts against a collar portion or abutment 12a of thebolt 12. The tensioning bolt 12 carries between its threaded end 16 andthe main portion a widened stop ring 25 which will abut against thecollar 11 to limit axial movement of the tensioning bolt member 12within the collar. The front or exterior end of the collar 11 isprovided with an annular recess or depression 26 which accommodates aregulator spring 27 which has a diameter which is located within thediameter of the tensioning spring 21. One end of the regulator spring isbent radially outwardly and then around the periphery of the tensioningdisks 22 and 23. The collar 11 is provided with a recess 44 toaccommodate the bent off end 28 of the regulator spring 27. The oppositeend 29 of the spring is inserted into a bore 30 which is defined in thecollar 11. A regulator ring 31 is arranged around the spring 27 in thesame recess of the collar 11 and it carries a ratchet 32 on which theend 28 of the spring 27 engages. The ring 31 becomes wedged in thedepression 26 by inherent tension. Ring 31 has a setting lug 33accessible from the outside of the tensioning device 54. This lug can bemoved in a recess 34 of the housing to set ratchet 32 in accordance withthe needle insertion. The tension of the regulator spring 27 is variedby resetting of the spring end 29 into a selected one of thecircumferentially spaced bores 30. This need be done only once.

The release of the thread tension occurs in a manner which is well knownthrough the action of a releasing bow 35 which is mounted on a bolt 36within the upper arm member 2. The bow 35 is actuated in a known mannerby a ventilating lever (not shown) of the sewing machine.

The needle thread which is designated by the numeral 37 is looped overthe tensioning bolt 12 and it engages around the bent arm portion 28 ofthe tensioning spring 27 when the thread giver 3 is moved to its highestposition so that the thread is tensioned and places itself against astop 38 of the collar member 11. Stop 38 is formed by the lateral edgesof a covering 39. In the embodiment illustrated, this covering 39 isformed integrally with collar member 11. The top of the covering 39 isprovided with a marking 40 as well as with symbols 41 and 42 for thesetting of stronger and weaker thread tension. Opposite the line marking40 on the regulating disk 4 there is a similar marking 43.

The thread tensioning device 54 operates as follows: After the correctthread tension has been adjusted the screw 13 is loosened and theregulating disk is rotated until the lines 40 and 43 are opposite eachother. The screw 13 is then tightened and the cover 56 is replaced onthe regulating disk 4. By rotating the regulating disk 4 in one or theother direction, the tension of the needle thread 37 is either increasedor decreased as desired. The rotation of the disk causes the movement ofthe tensioning nut along the threaded portion 16 so that the threadtension spring is either permitted to expand or retract to change thetension acting on the collar member and hence from the collar memberthrough the disks 22 and 23 and 24. In this manner, the tension on theneedle thread 27 is either increased or reduced accordingly.

When the thread giver 3 is moved into its highest position, the needlethread 37 will cause the bent-01f portion 28 of the regulator spring 27to move upwardly, that is, clockwise, as viewed in FIG. 4, into atensioned position. In this tensioned position, the thread will bearagainst the stop 38. During the descent of the thread giver 3, thebent-off arm portion 28 of the regulator spring 27 will bear against thethread and take away any slack. As the needle enters the material to besewn, the end 28 of the regulator spring will then place itself on theratchet 32 until the loop formation is completed and the needle threadis pulled up again.

It should be appreciated that the tensioning device 54 may be made witha collar portion 11 comprising a plurality of separate parts. The guidecam 18 for the ten sioning nut may be replaced by a pin, for example, ifdesired. The covering of the tensioning disk with the tension indicationmay be secured on the arm head 2 in a separate manner. Also theregulator spring 27 may lie either radially within the thread tensioningspring or radially outside thereof. With the construction set forthabove, the tensioning device 54 requires only a minimum of lateral andelevational space so that there is no interference with the visionaryfield of the operator.

While a specific embodiment of the invention has been shown anddescribed in detail to illustrate the application of the inventiveprinciples, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claim is:

1. A needle thread tensioning device comprising a collar member having acentral bore and including a tension disk end-face with an axiallyextending annular regulator spring recess defined therein and anopposite end face having a larger diameter axially extending tensionspring recess defined therein located radially outwardly from saidregulator spring recess, a shaft slidable and rotatable in the centralbore of said collar member, at least two tension members carried by saidshaft and having at least portions which are displaceable together toengage the thread, a collar on said shaft engaging said tension members,a thread regulating coil spring located within the regulator springrecess and bearing at its inner end against the interior of theregulating spring recess and having an outer end adjacent said tensionmembers and biased in a direction to engage the needle thread andtake-up any slack therein, a tension coil spring located in the tensionspring recess of said collar member and bearing against the inner end ofthe tension spring recess to urge said collar member against saidtension members to apply tension on said members and to the needlethread, and a nut member on said shaft and bearing against the outer endof said tension coil spring.

2. A needle thread tenisoning device, according to claim 1, includingmeans for shifting said nut member along said shaft for varying theforce on said tension coil spring and against said collar member andsaid tension members.

3. A needle thread tensioning device, according to claim 1, wherein saidtension members comprise a pair of disks mounted on said shaft, saidshaft having a threaded portion, said nut member being threaded onto thethreaded portion of said disk shaft and being capable of being advancedtherealong upon rotation of said shaft, means for holding said nutmember against rotation with said shaft when said shift is rotated, anda regulating knob carried on said shaft and exposed at the exteriorthereof and being rotatable to adjust the position of said nut member toregulate the tensioning on said tension coil spring.

References Cited UNITED STATES PATENTS 2,131,005 9/1938 Chason 242-2,518,703 8/1950 Marsac 242-150 2,701,694 2/1955 Hamlett 112-254 XR2,843,336 7/1958 Herbst 242-150 2,955,775 10/1960 Johnson 112-254 XRFOREIGN PATENTS 1,219,825 12/ 1959 France.

MERVIN STEIN, Primary Examiner GEORGE H. KRIZMANICH, Assistant ExaminerUS. Cl. X.R.

8/ 1942 Germany.

